Porous metal product and method of making same



1, 1941- A. J. LANGHAMMER ETAL 2,229,330

POROUS METAL PRODUCT AND METHOD OF MAKING SAME Filed March 8, 1937INVENTOR ANTHONY d LANGHAMMER M0 WILLIAM G. GAL/(INS. 4L!

fcza a -F ATTORNEYS man M 1941 '2 z29 330 uNi'rEo STATES PATENT OFFICE.

Anthony J. Langhammer and William G. Calkins,

- Detroit, Mich., assignors to Chrysler Corporation, Highland Park,Mich., a. corporation of Delaware Application March 8, 1937, Serial No.129,595

2 Claims. (01. 75-22) proved metal articles of this character which arepowdered metal of higher melting point, used in 5 of a porous nature andparticularly useful in frlcmanufacturing porous metal articles embodyingtion and anti-friction elements, such as bearings. the invention andmagnified approximately 172 One of the main objects of the invention isto times, the particular metal photograph being of improve the physicalcharacteristics, such as powdered sponge iron. 1o ductility and strengthof powdered metal prod- Fig. 5 is a perspective view of a bearing emuctsof this kind, by increasing the adhesion of bodylng the invention. I thepowdered metal particles to each other, and Powdered metal products ofthe type to :which particularly by increasing "the number of indlthisinvention relates. may be put to numerous vidual bonds between adjacentparticles of uses, but because of the porosity and lubricant powderedmetal. I absorbing capacity of such products, they are Another object ofthe invention is the provision particularly suitable for hearingpurposes. In of articles fabricated from a mixture of powdered general,products of this kind are manufactured metals having difierent meltingpoints, in which by thoroughly mixing together two or more the quantityof powdered metal of higher m'eltpowdered metals in selectedproportions. The ing point by far exceeds the quantity of powderedpowdered metals usually have diflerent melting metal of lower meltingpoint, but in which there points, and there is present a substantiallyare present substantially as many or more pargreater quantity of thepowdered metal of higher ticles of the powdered metal of lower meltingmelting point than that of the lower melting point. j point. In additionto the powdered metals, which Further objects of the invention are toprovide constitute the main constituents of the mixture, articles ofthis character in which there are there may be added relatively smallquantities of present at least one particle of the powdered solidlubricants such as graphite, which it may metal oi lower melting pointto bond each par-- be desired to retain in the final product. The ticleof powdered metal of higher melting point mixture may also containvolatile or other lubrito the next adjacent similar particle; to providea cants which are mainly removed during the sinmixture of such powderedmetals in which the tering operation, thesematerials being providedparticles of lower melting point aresubs'tantially to lubricate thesurfaces of the dies or molds in smaller than those of higher meltingpoint; and which the powdered mixture is compressed. to provide acompressed and sintered powdered The powdered constituents of themixture are metal structure which has substantially each parthoroughlyincorporated together and distributed ticle of metal of higher meltingpoint bonded to 7 throughout each other by a suitable mixing opereachadjacent particle of similar metal by a paration and they are thencompressed under high ticle of the metal of lower melting point. unitpressure into briquettes of desired shape.

An illustrative embodiment and diagrammatic The briquettes are thenremoved from the die and 40 explanation of the invention is shown in theacsintered, preferably in a reducing or non-oxidizcompanying drawing, inwhich: ing atmosphere, at a temperature above the melt- Flg. 1 is.adiagrammatic illustration of the aping point of the powdered metal oflower melting proximate relationship and comparative size of temperatureand below the melting temperature particles of powdered metal includedin powdered of the metal of higher melting point. During metal mixturesused in manufacturing articles this sintering operation, the particles01 metal of embodying the invention. highermelting point are bondedtogether by the Fig. 2 is a diagrammatic illustration of the apparticlesof metal of lower melting point. proximate relationship and relativesize of the -For the purpose of illustration, powdered iron articles ofpowdered metal conventionally used in and powdered copper particles areshown in the the manufacture of compressed and sintered drawing,although combinations of other metals bearing products. Y ,of differentmelting points may he used to equal Fig. 3 isa sketch of amicro-photograph of the advantage in the practice of the invention.

powdered metal of lower melting point, used in In Fig. 1 of the drawing,there is diagramm nllf ul Porous bearing articles embodymaticallyillustrated the relationship and relative a This invention relates toimprovements in compressed and sintered powdered metal articles and ingthe invention and magnified approximately 172 times, the particularmetal photographed being copper.

Fig.4 is a sketch of a micro-photograph of the the illustration shown,there are nine large circles Ill, which represent particles of powderediron, and ten small circles H, which represent particles of powderedcopper. Each particle of powdered iron is shown to be approximately ofthe order of ten times as large as a corresponding particle of powderedcopper Ii, this illustration being diagrammatically illustrative of therelative average sizes of a large number of particles. This figureapproximately represents the relative size of the particles of iron andcopper in a mixture comprising substantially ten percent copper andninety percent iron, the size of the particles being illustrative of thequantity by weight thereof.

By thoroughly mixing the powdered metal, an arrangement thereofcorresponding approximately to the diagrammatic illustration shown inFig. l is obtainable. Each particle of iron Ill has between it and thenext successive particle of iron a small particle of copper i I and bypredetermining the sizes of the particles such that there is a greaternumber of particles of copper than particles of iron, an extra particle,or extra particles of copper may be provided in a central location withrespect to the particles of iron. When the particles of a mixture ofpowdered iron and powdered copper are arranged in a manner approachingthat illustrated in Fig. 1, and the mixture is then compressed andsintered, the particles of powdered copper between adjacent particles ofpowdered iron fuse and provide bonds between the iron particles. Thecentrally located particle of powdered copper also fuses to provideadditional bonds between all of the particles of powdered iron withwhich it is associated. In this manner, each particle of powdered ironis rigidly bonded to an adjacent particle of powdered iron by severalcopper bonds.

When the particles of powdered copper are substantially the same size asthe particles of powdered iron, as illustrated in Fig. 2, or larger thanthe iron particles, the number of bonds between the particles ofpowdered iron resulting from the sintering operation is materially lessthan the number of bonds provided by the invention.

From a consideration of the micro-photograph shown in Figs. 3 and 4, itis obvious that a mathematically accurate and precise relationship ofsizes of powdered metals of different melting tem- 'peratures andarrangement thereof, such as that shown in Fig. 1, cannot be obtained,but by properly predetermining the size of the metals of differentmelting points and taking into account the quantity and density thereof,it is possible to approach or approximate the arrangement and relativesizes illustrated in this figure. In general, it is sufficient to obtainmeritorious results from practice of the invention if the particles ofmetal of lower melting point are present in number of substantially thesame order as the number of particles of metal of higher melting point.When this condition exists, the resulting bearing I4, shown inperspective in Fig. 5, has all of its powdered metal particles rigidlybonded together by a much larger number of bonds than have beenheretofore provided and the porous structure is therefore lesssusceptible'to fracture and capable of withstanding greater loads. Theincreased number of bonds betweenv the metal particle resuits in anincrease in both structural strength and ductility of the finishedproduct.

The powdered metals should preferably have the following screenanalysis:

Iron particles All through 150 mesh Approximately will be collected onscreens of between 150 and 325 mesh Approximately-25% through 325 mesh.

Ninety percent of the powdered copper particles should be capable ofpassing through a 325 mesh screen.

This invention may be practiced in the formation of porous productsmanufactured from mixtures of powdered materials having the followingcompositions:

Regardless of the particular proportions and nature of the constituentsof mixtures of powdered material from which porous metal products may beformed, predetermining of the size of the particles of higher meltingpoint with respect to the particles of metal of lower melting point inaccordance with this invention, will result in the attainment ofsuperior structural properties in the final products formed from themixture.

Although but several specific embodiments of the invention is hereinshown and described, it will be understood that various changes in thesize, shape and arrangement of parts may be made without departing fromthe spirit of our invention.

We claim:

1. A sintered porous bearing structure comprising substantially byweight of powdered iron and substantially 10% by weight of powderedcopper particles, the particles of powdered copper being fused toadjacent particles of powdered iron for providing a substantially fusedbond therebetween and being of such order of size that when unfusedsubstantially 90% thereof will pass through a 325 mesh screen and saidparticles of powdered iron being of such order of size thatsubstantially all thereof will pass through a mesh screen, substantially75% thereof will be collected on screens of between 150 to 325 mesh andsubstantially 25% thereof will pass through a 325 mesh screen.

2. The method of making a porous metal bearing structure which comprisescompressing into a briquette a mixture comprising substantially 10% byweight of powdered copper and 90% by weight of powdered iron, theparticles of powdered iron being of an average size in volumeapproximately ten times that of the average size in volume of theparticles of powdered copper, and sintering said briquette in anon-oxidizing atmosphere at a temperature between the meltingtemperature of said powdered iron and said powdered copper for formingfused bonds between portions of adjacent particles of said powderediron.

ANTHONY J. LANGHAMMER. WILLIAM G. CALKINS.

